configure.ac (gcc_cv_ld): Prefer in-tree ld over whatever the top-level detects...

* configure.ac (gcc_cv_ld): Prefer in-tree ld over whatever the
top-level detects, except when in-tree ld is being cross-built.
(gcc_cv_as): Likewise for as.  Use AS_FOR_TARGET otherwise, and
then AS only if target is host.
* configure: Rebuilt.

From-SVN: r82258